Dell Inspiron 530 Freeze on Startup

This computer belongs to my mother who's a long time Dell fan and user so I am unsure of what happened to it to make it start this way, as I wasn't there when it happened.
The computer started freezing about 3mins after start up then started freezing sooner and sooner, now it freezes after the BIOS page. I've tried checking every connection inside and out of the computer, everything seems fine, I unplugged everything I could and plugged it all back in, hard drive, DVD player etc, etc. I was able to enter the setup menu but after leaving it froze again. I don't think it's hardware failure, but it could be I guess, I've never had a CPU fail on me, so maybe that's the problem? I don't know. Are there any known viruses that match this? Any help would be appreciated.


System Specs (as far as I can remember)


Dell Inspiron 530
OS: Windows 7 32bit (Not original, original was Windows XP pro)
RAM: 4GB (Windows 7 only sees 3.3GB or whatever, of course)
Hard Drive 650GB (I think, I'd have to take it out to get any more info)
GPU: Radeon HD 5670 (Not original)
Peripherals are all newer Dell products.